/*
 * Copyright [2013-2021], Alibaba Group Holding Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.calcite.rel.rules;

/**
 * A rule that implements this interface indicates that the new RelNode
 * is typically better than the old one. All the substitution rules will
 * be executed first until they are done. The execution order of
 * substitution rules depends on the match order.
 */
public interface SubstitutionRule extends TransformationRule {

    /**
     * Whether the planner should automatically prune old node when
     * there is at least 1 equivalent rel generated by the rule.
     *
     * <p>Default is false, the user needs to prune the old node
     * manually in the rule.</p>
     */
    default boolean autoPruneOld() {
        return false;
    }
}
